Among all word pairs with confusing meanings and uses, i.e. and e.g. occupy a peculiar position. They are identical especially because they are two-letter abbreviations. They are, however, not to be used interchangeably because their meanings are different.
To start with, i.e. is the abbreviation of the Latin phrase ‘id est’, which means ‘that is’ or ‘in other words.’ On the other hand, e.g., also a Latin expression, refers to ’exempli gratia’, meaning, ‘for example’. With i.e, we explain, restate or emphasise what has been said but, with e.g, we cite the examples of a particular element or occurrence. Consider the difference in the following examples:
I need a car, i.e. something good enough to regularly take me from Abuja to Kaduna.
Many politicians were present, e.g. Chief John Nnadi and Alhaji Dauda Gumsu.
In the above clauses, while i.e. gives further information about the desired car in the first sentence, e.g introduces examples of the politicians present, in the second..
Difference in scope
Another major difference between the two terms is that when you use i.e., you somehow re-present the entirety of the original/initial statement. The element that the i.e. introduces usually restates or reflects the whole of the first expression. When you use e.g., however, you normally only list parts of the examples. There will be others (examples) you cannot exhaustively capture at that moment:
Many social events hold in Lagos by the end of the year, i.e. October to December.
Lagos is the place to be for many dreamers, i.e. many folks desirous of socioeconomic breakthrough.
England played against several other countries during the competition, e.g. Slovakia and Netherlands.
Spain paraded many young players, e.g. Lamine and Williams.
Need for commas and parenthesis
To avoid structural confusion, you should use punctuation marks like commas, brackets and dashes to delineate i.e. and e.g.:
Many countries are participating in the Olympic Games, i.e. those that qualified from their different continents.
Many countries are participating in the Olympic Games, e.g. Nigeria, Ghana, France and Spain.
Many countries are participating in the Olympic Games (i.e. those that qualified from their different countries) as the reported noted.
Many countries are participating in the Olympic Games (e.g. Nigeria, Ghana, France and Spain) as the reporter noted.
Between ‘including’ and ‘e.g.’
The function of ‘including’ is similar to that of ‘e.g.’ in the sense that it also connotes ‘for example’. This, however, further suggests that it is a part of the things you have in mind that is involved when you use ‘including’. That is why some speakers/writer still labour to say ‘including, but not limited to’ when speaking or writing:
Many countries are participating in the Olympic Games (e.g. Nigeria, Ghana, France and Spain) as the reporter noted.
Many countries are participating in the Olympic Games (including Nigeria, Ghana, France and Spain) as the reported noted.
Dash vs i.e.
The dash can work with i.e. but it can also entirely replace it (i.e.). The reason is that the punctuation mark ntroduces additional information:
I need a good rest — i.e. after the competition.
I need a good rest — after the competition.